Submitted by Emanuel Varela Cardoso (emanuel.varela@ufcg.edu.br) on 2018-06-22T18:16:20Z No. of bitstreams: 1 JÉSSICA CAMILLA DA COSTA LIMA – DISSERTAÇÃO (UAEMa) 2016.pdf: 6436164 bytes, checksum: 0eb0aed4e907b380df345b619174c509 (MD5) / Made available in DSpace on 2018-06-22T18:16:20Z (GMT). No. of bitstreams: 1 JÉSSICA CAMILLA DA COSTA LIMA – DISSERTAÇÃO (UAEMa) 2016.pdf: 6436164 bytes, checksum: 0eb0aed4e907b380df345b619174c509 (MD5) Previous issue date: 2016-02-24 / Capes / Com o intuito de superar algumas limitações do poli(ácidolático) (PLA), foi feita sua mistura com o copolímero poli(estireno/etileno-butileno/estireno) (SEBS), em diferentes concentrações e avaliadas diversas propriedades. As blendas contendo 5,10, 15 e 20% em massa do SEBS foram preparadas por extrusão seguida de injeção e caracterizadas por ensaios reológicos, difratometria de raios X (DRX), espectroscopia na região do infravermelho com transformada de Fourier (FTIR), calorimetria exploratória diferencial (DSC), análise térmica dinâmico-mecânica (DMTA), temperatura de deflexão térmica (HDT), propriedades mecânicas e a morfologia foi investigada por microscopia eletrônica de varredura (MEV). Estas propriedades foram avaliadas antes e após tratamento térmico de recozimento. Os resultados de reometria de torque indicaram que as blendas apresentam maior estabilidade quando comparadas ao PLA puro. Em baixas frequências (reômetro oscilatório) o PLA e as blendas PLA/SEBS contendo 5 e 10% de SEBS apresentam um comportamento de fluido newtoniano, já as blendas contendo 15 e 20% apresentam um comportamento de fluido pseudoplástico, observa-se também a presença de dois arcos distintos para todas as blendas, indicando que as fases de PLA e SEBS são imiscíveis. Verifica-se para as blendas PLA/SEBS contendo 15 e 20% de SEBS, há uma mudança na inclinação das curvas, esta mudança indica que as mesmas passam a apresentar um comportamento de pseudo-sólido. Nos padrões de DRX das amostras submetidas ao tratamento térmico de recozimento observa-se um pico intenso e bem definido caracterizando cristalinidade considerável das amostras. As análises de DSC e DMTA indicaram que com tratamento térmico ocorreu o desaparecimento da temperatura de cristalização a frio (Tcc) doPLA. As amostras recozidas apresentaram valores de HDT mais elevados. Observou-se um balanço de propriedades mecânicas, no qual o módulo elástico e a resistência à tração tiveram uma pequena redução para as blendas sem tratamento e aumento destas propriedades com tratamento térmico, enquanto que o alongamento, a tenacidade e resistência ao impacto tiveram aumento significativo para as amostras sem e com tratamento térmico. Os resultados de MEV indicaram que com o aumento da concentração do copolímero observa-se aumento do tamanho médio das partículas, provavelmente devido à ocorrência de coalescência. Os resultados de MEV após tratamento térmico em geral, pode-se observar um refinamento no tamanho médio das partículas 7 dispersas de SEBS que influenciou nas propriedades mecânicas. As blendas estudadas no presente trabalho apresentam propriedades muito atrativas, contendo pequenas quantidades do copolímero sintético. Omaterial desenvolvido advém, em sua maior proporção, de fontes renováveis, contribuindo assim, com o meio ambiente. / In order to overcome certain limitations of poly (lactic acid) (PLA) biopolymer, the same was modified with poly (styrene / ethylene-butylene / styrene)(SEBS) copolymer, and the effect of different content of this copolymer on the properties of the blends, before and after heat treatment, was evaluated. The blends containing 5, 10, 15 and 20 wt% of SEBS were prepared by extrusion followed by injection molding and characterized by rheological measurements, X-ray diffraction (XRD) Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA) and heat deflection temperature (HDT). The results of torque rheometry indicated that the blends exhibited increased stability compared to pure PLA. At low frequencies (oscillation rheometer) PLA and PLA / SEBS blends containing 5 and 10% of SEBS exhibited a Newtonian fluid behavior, and the blends containing 15 and 20% SEBS showed a shear thinning behavior. It was also observed the presence two distinct arcs for all blends, indicating that the SEBS and PLA phases are immiscible. It was also observed that in the PLA / SEBS blends containing 15 and 20% SEBS, there is a change in the slope of the curves. This change indicates that they begin to present a pseudo-solid behavior. In the XRD patterns of the samples subjected to annealing heat treatment a well-defined intense peak was observed for PLA indicating its considerable crystallinity in the samples. The FTIR analysis pointed out, by the presence of characteristic bands, that the PLA presented higher crystallinity after the annealing heat treatment. The annealed samples showed higher HDT values. There was a balance of mechanical properties, wherein the elastic modulus and the tensile strength proved to be inversely proportional to the content of the copolymer, while the elongation and tenacity were directly proportional to this content. The addition of the copolymer caused a significant increase in the impact strength for samples with and withoutheat treatment. The SEM results showed that when the SEBS copolymer content was increased, an increase in the average particle size of SEBS dispersed phase was observed, probably due to the occurrence of coalescence. SEM results for samples after heat treatment showed a decrease in average size of dispersed particles of SEBS, which affected the mechanical properties. The blend studied in this paper presented very attractive properties, and contains small amounts of the synthetic 9 copolymer. The developed material comes, in its most proportion, from renewable sources, thus contributing to the environment.

Made available in DSpace on 2016-08-17T18:39:30Z (GMT). No. of bitstreams: 1 2145.pdf: 2206472 bytes, checksum: 5295597725f34bdf5560d6cda8af7446 (MD5) Previous issue date: 2008-03-27 / Financiadora de Estudos e Projetos / Streptococcus pneumoniae (pneumococo) is a pathogenic bacterium that causes several infections which are aggravated by the increase of serotypes with antibiotics resistance. The development of an effective vaccine against this pathogen is crucial for the prevention of the neumococcal illnesses. Conjugated vaccines, consisting of the capsular polysaccharide joined to a carrier protein, are more efficient in the stimulation of the immunologic memory. The capsular polysaccharide (PS) is present in the capsule that involves the cell. Thus, the conjugated vaccine elaboration involves bacterial cells cultivation for its production. As the organism is cultivated in the oxygen absence, the lactate production is inevitably high, leading to growth inhibition due to lactate accumulation in the medium. To minimize the inhibitory effects of the lactate accumulation and to increase the PS production it is necessary to monitor the process and adequately control the addition of supplementary medium along with the withdrawal of saturated medium. This kind of operation can be performed by carrying out a fed-bath cultivation in a bioreactor connected to a perfusion system. The success on the monitoring, control and optimization of this bioprocess depends on the efficiency of the modeling and simulation resources employed. This research work considers the uses intelligent computational techniques, specifically the technique of heuristical search called simulated annealing (SA) combined with neural networks for the state inference and the optimization of S. pneumoniae cultivations. The proposal was implemented as a computational system that: a) uses the SA for the identification of the values for a set of parameters associated to unstructured models and; b) uses neural networks (individually and grouped as a committee) for the state inference of a culture. The work presents and discusses the results of the system for data sets experimentally obtained and highlights the importance of the proposal for achieving a higher efficiency in the culture control processes. / Streptococcus pneumoniae (pneumococo) é uma bactéria patogênica causadora de várias infecções que são agravadas pelo aumento de cepas com resistência aos antibióticos. O desenvolvimento de uma vacina efetiva contra este patógeno é crucial para a prevenção das doenças pneumocócicas. Vacinas conjugadas, constituídas pelo polissacarídeo capsular ligado a uma proteína carregadora, são mais eficientes no estímulo da memória imunológica. O polissacarídeo capsular (PS) está presente na cápsula que envolve a célula e, desta forma, a elaboração de vacinas conjugadas envolve o cultivo da bactéria para a produção do mesmo. Como o microrganismo é cultivado na ausência de oxigênio, a produção de lactato é inevitavelmente elevada e o seu acúmulo no meio provoca a inibição do crescimento. Para minimizar os efeitos inibitórios da acumulação de lactato e aumentar a produção de PS é necessário monitorar o processo e controlar adequadamente a adição de meio suplementar e a retirada de meio saturado em cultivos operados em batelada alimentada, utilizando biorreatores acoplados a sistema de perfusão. O sucesso no monitoramento, no controle e na otimização deste bioprocesso depende da utilização de recursos de modelagem e de simulação que sejam eficientes. Este trabalho de pesquisa propõe o uso de técnicas computacionais inteligentes, especificamente a técnica de busca heurística chamada de simulated annealing (SA) aliada a redes neurais, para a inferência de estado e a otimização de cultivos de S. pneumoniae. A proposta foi concretizada via desenvolvimento de um sistema computacional que: a) faz uso do SA para a identificação do conjunto de valores de parâmetros associados a modelos não estruturados e; b) usa redes neurais (individualmente e em regime de comitê) para a inferência de estado de um cultivo. O trabalho apresenta e discute os resultados do sistema em conjuntos de dados obtidos experimentalmente e evidencia a importância da proposta para uma maior eficiência no controle de processos de cultivo.

Submitted by Élida Maeli Fernandes Quirino (maely_sax@hotmail.com) on 2018-05-15T18:41:41Z No. of bitstreams: 1 MARIA CLIMENE BEZERRA DE MEDEIROS ALMEIDA - DISSERTAÇÃO PPGSA PROFISSIONAL 2013..pdf: 1751447 bytes, checksum: 7b509cf8dc0cbea4081ecc56f10efd4b (MD5) / Made available in DSpace on 2018-05-15T18:41:41Z (GMT). No. of bitstreams: 1 MARIA CLIMENE BEZERRA DE MEDEIROS ALMEIDA - DISSERTAÇÃO PPGSA PROFISSIONAL 2013..pdf: 1751447 bytes, checksum: 7b509cf8dc0cbea4081ecc56f10efd4b (MD5) Previous issue date: 2013 / Os frutos da bananeira representam o quarto maior produto mais importante comercializado no mundo. O Brasil, um dos maiores produtores mundiais de banana, é também um dos que apresenta maior desperdício. Visando à diminuição dessas perdas, a banana ainda verde, vem sendo considerada como um produto ideal para ser industrializado, por conter uma grande quantidade de amido, sendo parte desse amido considerado amido resistente com efeitos fisiológicos similares aos da fibra alimentar. Assim, esse trabalho objetiva extrair o amido da banana verde (Musa AAB, Prata) e modificar hidrotermicamente por dois métodos distintos. A partir dos amidos obtidos, avaliar as propriedades funcionais e sua possível utilização como ingrediente no processamento de alimentos. Para a extração do amido a polpa da banana verde foi tratada com solução de bissulfito 1%. Para a modificação hidrotérmica por Tratamento Térmico em Baixa Umidade (TTBU), a umidade do amido foi ajustada para 15%, 20% e 25%. Para a modificação por annealing (ANN), o amido foi tratado com excesso de água em banho-maria em temperaturas de 45, 50 e 55 ºC por 16 horas. O amido nativo e os amidos modificados foram analisados físico-quimicamente e os resultados comparados ao amido de milho. As propriedades funcionais também foram analisadas. O rendimento de extração foi de 23,80%, com boa qualidade. O teor de amido resistente com a modificação por TTBU 25% foi reduzido em relação ao amido nativo de 24,92% para 20,74% e, aumentou com a modificação por ANN 50 ºC para 26,95%. O TTBU 25% aumentou o teor de amilose em relação ao amido nativo de 42,13% para 47,10%, já o ANN 50 ºC reduziu este componente para 38,60%. O poder de intumescimento (PI) foi reduzido nos amido modificados por TTBU. O ANN aumentou o PI dos amidos a 70 ºC. Os amidos da banana verde mostraram-se menos solúvel que o amido de milho comercial. O TTBU 25% aumentou a capacidade de absorção de água (CAA) em 34,85% e a capacidade de absorção de óleo (CAO) em 14,20% em relação ao amido nativo. O ANN 50 ºC reduziu o CAO em 3,55%. As modificações aumentaram a concentração mínima de formação de gel (GLC), sendo registrado aumento de 6% (amido nativo) para 12% (TTBU 25%). Todos os amidos modificados apresentaram claridade da pasta superior aos valores apresentados pelo amido nativo de banana. Os tratamentos hidrotémicos promoveram redução na sinérese, sendo essa redução mais acentuada para o amido modificado por ANN 55ºC com redução de 45,22% em relação ao amido nativo. Com o ANN os amidos passaram a ter sinérese semelhante ao amido de milho comercial, analisado para fins de comparação. Considerando-se a qualidade, o rendimento de extração, o teor de amido resistente e as propriedades funcionais que apresentaram variados resultados frente às modificações. Pode-se concluir que o amido proveniente da banana verde ‘Prata’ é viável tecnologicamente, podendo servir de ingrediente em variados segmentos da indústria alimentícia. / Banana fruits represent the fourth largest most important product commercialized worldwide. Brazil is one of the largest banana producers in the world and is also one of the countries that waste the most. Aiming to reduce wastage, green banana has been considered an ideal product to be industrialized, because it contains a large amount of starch, which part of it is considered resistant starch, with physiological effects similar to those of alimentary fiber. Given this, the present work aims to extract starch from green banana (lady’s finger kind) and modify it hydrothermally by two distinct methods. From the starches obtained were evaluated the functional properties and their possible use as an ingredient in food processing. For the extraction of the starch, the green banana pulp was treated with bisulfite solution 1%. For hydrothermal modification by heat moisture treatment (THM), the starches had their moisture adjusted to 15%, 20% and 25%. For modification by annealing (ANN), the starch was treated with excess of water in a water bath at temperatures of 45, 50 and 55 ºC for 16 h. The native and modified starches were analyzed physico-chemically and the results were compared with the corn starch. The functional properties were also analyzed. The extraction yield was 23.80%, with good quality. The resistant starch content with the modification by THM 25% got reduced compared to the native starch from 24.92% to 20.74% and increased with the modification by ANN 50 ºC to 26.95%. The THM 25% increased amylose content compared to native starch from 42.13% to 47.10%, while the ANN 50 °C reduced it to 38.60%. The swelling power (SP) was reduced in starch modified by THM. The ANN increased the SP of the starches at 70 °C. The green banana starches were less soluble than commercial corn starch. The TTLH 25% increased the capacity of water absorption (CWA) in 34.85% and the oil absorption capacity (OAC) in 14.20% compared to native starch. The ANN 50 °C reduced the OAC in 3.55%. The modifications increased the minimum concentration of gel formation (CGF) and recorded increase of 6% (native starch) to 12% (THM 25%). All modified starches showed pulp clarity greater than the values for banana native starch. The hydrothermal treatments promoted a reduction in syneresis and this reduction was more pronounced in the starch modified by ANN 55 ºC, with a reduction of 45.22% compared to the native starch. After the ANN, the starches obtained syneresis similar to commercial corn starch, analyzed just for comparison. Considering quality and yield of extraction, resistant starch content and functional properties that showed varied results after modifications, it was concluded that the starch from the green banana (lady’s finger kind) is technologically feasible and it can be used as an ingredient in various segments of the food industry.

De maneira a melhorar o desempenho de um Transistor de Efeito de Campo Metal-Óxido-Semicondutor (MOSFET), o germânio (Ge) é um forte candidato para substituir o silício (Si) como semicondutor, devido a sua alta mobilidade dos portadores de carga. Contudo, o filme de dióxido de germânio (GeO2) sobre Ge é solúvel em água e suas propriedades elétricas inferiores. Nesse sentido, a proposta desta dissertação de Mestrado é oxinitretar termicamente filmes de GeO2 em atmosfera de óxido nítrico (15NO), de maneira a melhorar as propriedades elétricas e físico-químicas dessas estruturas. Inicialmente, as amostras foram limpas quimicamente usando uma mistura de peróxido de hidrogênio (H2O2) e ácido clorídrico + água (HCl + H2O, 4:1). Os filmes de GeO2 foram crescidos termicamente sobre Ge usando atmosfera de oxigênio enriquecido 97% no isótopo de massa 18 (18O), com parâmetros na qual geraram um filme com espessura de ~5 nm. As oxinitretações foram realizadas em um forno térmico rápido com atmosfera de 15NO, nas temperaturas variando de 400-600°C, nos tempos de 1 a 5 minutos. O objetivo da oxinitretação foi criar um filme de oxinitreto de germânio (GeOxNy) com propriedades físico-químicas satisfatórias para a indústria de microeletrônica. Também foram realizados recozimentos térmicos em atmosfera inerte com objetivo de testar a estabilidade térmicas dos filmes de GeOxNy. Análise com Reação Nuclear (NRA) e Espectrometria de Retroespalhamento Rutherford em geometria de canalização (RBS-c) foram utilizadas para quantificar a quantidade total de oxigênio 18O e 16O, respectivamente. NRP também foi utilizada de modo a determinar o perfil de concentração em função da profundidade para as espécies de 18O e 15N. De modo a investigar a composição química das amostras, Espectroscopia de Fotoelétrons induzidos por raio-X (XPS) foi utilizada. Pelas análises por RBS e NRA do 18O, podemos observar que ocorre troca entre os isótopos de 18O e 16O para todas das temperaturas de oxinitretação. Este resultado corrobora com estudos recentes da literatura. Para as amostras oxinitretadas em 5 minutos a 500°C e todas as amostras oxinitretadas a 550°C e 600°C, ocorre troca isotópica completa. Observamos ainda por NRP que o 15N é incorporado mais superficialmente para as temperaturas de oxinitretação até 550°C. Resultados de XPS indicam formação maior de GeOxNy próximos da superfície das amostras e para temperaturas e/ou tempos maiores. Testes de estabilidade térmica indicam que a incorporação de nitrogênio mais próximo das superfície da amostra inibe a dessorção das espécies de GeO. As amostras que não foram oxinitretadas acabam dessorvendo quase por completo o filme de GeO2 quando realizados os recozimentos térmicos. Este efeito do nitrogênio incorporado próximo da superfície tem grande potencial para uso em camadas interfaciais entre semicondutor e dielétricos de porta. / In order to improve the performance of Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET), germanium is a good candidate to replace silicon as semiconductor due to its higher charge carrier mobility. However, the germanium dioxide (GeO2) film over Ge is water soluble and produces poor electrical characteristics. In this way, this Master dissertation proposes thermal oxinitridation of the GeO2 films in nitric oxide (15NO) atmosphere in order to improve its electrical and physico-chemical characteristics. Samples were first cleaned using a mixture of hydrogen peroxide (H2O2) and hydrogen chloride + water (HCl + H2O, 4:1). GeO2 films were thermally grown on Ge using oxygen enriched in 97% in the isotope of mass 18, which generated ~5 nm thick film. Oxinitridation was performed in a rapid thermal furnace under 15NO atmosphere, at the 400-600°C temperature range, and 1-5 minutes time range. The goal was to form a germanium oxinitride film (GeOxNy) with physico-chemical properties that are satisfactory for microelectronics industry. We also performed thermal annealing in inert atmosphere to test the thermal stability of GeOxNy films. Nuclear Reaction Analysis (NRA) and Rutherford Backscattering Spectrometry in channeled geometry (RBS-c) were used to quantify the total amount of oxygen 18O and 16O, respectively. NRP was also performed to determine the 18O and 15N depth distribution. In order to investigate the chemical composition of the samples, X-ray Photoelectron Spectroscopy (XPS) was performed. RBS and NRA analysis showed isotopic exchange between 18O and 16O for all temperatures investigated. This result corroborates previous literature studies. Samples oxynitrided in 5 minutes at 500°C and all the samples oxinitrided at 550-600°C showed complete isotopic exchange. We also observed by NRP that nitrogen incorporation occurs more superficially until 550°C. XPS results indicate more formation of GeOxNy near the surface of the samples and for higher temperatures and/or time of oxinitredation. Thermal stability results indicated that the nitrogen incorporation near the sample surface inhibit the GeO desorption. On the other hand, samples that were not oxynitrided have almost all the GeO2 desorbed when thermal annealing is performed.

Le collage par adhérence moléculaire est un collage basé sur la mise en contact de deux surfaces sans l'utilisation de colle ou matériaux additionnels. Ce procédé de collage est utilisé dans de nombreuses applications, notamment dans les domaines de l'optique terrestre et spatiale. Bien qu'un prototype ait déjà passé avec succès l'environnement spatial - où les contraintes d'utilisations sont différentes de celles rencontrées sur Terre - la spatialisation de cette technologie nécessite une caractérisation plus fine du procédé ainsi qu'une amélioration de la tenue mécanique des interfaces adhérées afin de valider les normes de l'Agence spatiale Européenne. Pour répondre à cette problématique de spatialisation de la technologie, des essais mécaniques ainsi que des analyses chimiques ont été réalisés dans le but d'étudier l'influence de certains paramètres du procédé ) sur la tenue mécanique et l'énergie de collage. Ces essais ont également été réalisés afin de comparer les deux matériaux étudiés : le verre de silice et le Zérodur vis-à-vis de l'adhésion. A l'issue de ces essais, les paramètres à appliquer permettant de doubler la tenue mécanique des interfaces adhérées ont été déterminés. Parallèlement, une loi phénoménologique reliant l'énergie de collage aux précédents paramètres du procédé a été développée ainsi qu'un modèle macroscopique visant à décrire l'intensité d'adhésion. Ces deux modèles une fois couplés permettent de modéliser le comportement normal de l'interface en fonction des paramètres du procédé. Enfin, ces deux lois sont implémentées dans un code éléments finis afin de simuler la propagation de la fissure lors de l'essai de clivage au coin. / Direct bonding consists in joining two surfaces without the use of any adhesive or additional material. This process is used in several applications, particularly in terrestrial and spatial optics. Although a prototype passed with success spatial environment - where constraints involved are very different from those encountered on Earth - this technology requires a more detailed characterization and an improvement of the mechanical strength of bonded interfaces in order to validate the European Space Agency standards. To address this issue, mechanical tests (double shear tests, cleavage tests and wedge tests) and chemical analysis (wetting tests and XPS spectroscopy) were performed in order to study the influence of some process parameters (roughness, relative air humidity during room temperature bonding, the annealing temperature and time) on the mechanical strength and the bonding energy. These tests compared the two materials used: fused silica glass and Zerodur glass. As a result of these tests, optimal parameters doubling the mechanical strength were also obtained. In the same time, a phenomenological law relating the bonding energy to the previous parameters is developed as well as a macroscopic model to describe the adhesion intensity. Both models when coupled describe the normal behavior of the bonded interface depending on the process parameters. Then, the both laws are implemented in a finite elements model in order to simulate the crack propagation during the wedge test.

La thèse s'inscrit dans le cadre du projet GENOME « Gestion Optimisée de l'Energie » dont l'enjeu majeur est la conception d'un avion plus électrique. L'augmentation de l'efficacité énergétique et de la compacité des systèmes électriques de ces avions entraîne de fortes sollicitations en température. Ces sollicitations sont liées à la compacité des systèmes (réduction de masse et de volume) ainsi qu'à leur localisation par rapport aux sources chaudes (réacteur d'avion par exemple). De ce fait, les matériaux magnétiques des nouveaux convertisseurs électriques doivent pouvoir fonctionner sous des conditions de hautes températures, supérieures à 200°C. Il s'agit du polycristallin FeCoV dédié à la fabrication des tôles du stator et du rotor des génératrices rapides (situées à proximité des réacteurs) et le nanocristallin FeCuNuSiB dédié à la conception des inductances et transformateurs des convertisseurs statiques. Ce manuscrit s'intéresse à l'étude du vieillissement thermique de ces deux familles de matériaux magnétiques. Ces matériaux, fournis par la société APERAM, se déclinent sous plusieurs nuances et finitions. L'étude du vieillissement consiste en l'application de plusieurs essais de vieillissement continus sous différentes températures (jusqu'à 300 °C pour les FeCoV et 240 °C pour les nanocristallins). Plusieurs grandeurs macroscopiques magnétiques, électriques et mécaniques (pour les FeCoV) sont mesurées à chaque intervalle de vieillissement. Grâce à ces mesures macroscopiques et à des mesures complémentaires effectuées à l'échelle microscopique, des analyses sont faites et des hypothèses sont proposées afin d'expliquer les mécanismes de vieillissement de ces deux familles de matériaux et dans le but de proposer des modèles phénoménologiques fiables / The thesis takes part of the project GENOME “Gestion Optimisée de l’Energie” whose major issue is the design of the more electrical aircraft. The increase in the energy efficiency and the compactness of the electrical systems of these aircrafts lead to high temperature stresses. These thermal stresses are related to the compactness of the systems (reduction of mass and volume) as well as their location with respect to the hot sources (aircraft engine for example). Thus, the magnetic materials of the new electrical converters must be able to operate under conditions of high temperatures, above 200 °C. Typically, the FeCoV polycrystalline materials are dedicated to the fabrication of the stator and rotor sheets of the fast generators (located near the aircraft engine) and the FeCuNbSiB nanocrystalline materials are dedicated to the design of inductors and transformers of the static converters.This manuscript concerns the thermal ageing study of these two magnetic material families. These materials, supplied by the company APERAM, are available in several shades. The ageing study consists on applying several continuous ageing treatments at different temperatures (up to 300 °C for FeCoV and 240 °C for FeCuNbSiB). At each ageing step, several macroscopic properties namely: magnetic, electrical and mechanical (for the FeCoV materials) properties are measured. Using these macroscopic properties and complementary measurements carried out on a microscopic scale, analyses are made and hypotheses are proposed in order to explain the ageing mechanisms of these magnetic material families. The understanding of the magnetic ageing mechanisms is necessary towards establishing of phenomenological ageing models

Die Temperung mittels Xenon-Blitzlampen (Flash Lamp Annealing - FLA) ist ein Kurzzeittemperverfahren mit Pulszeiten im Bereich von Millisekunden, bei dem nur die Oberfläche eines Substrats erhitzt wird. Durch die Blitzlampentemperung kann der Schichtwiderstand von tansparenten leitfähigen Oxidschichten reduziert und die Transmission im sichtbaren Licht erhöht werden. In dieser Arbeit wurde dies am Beispiel von Indium-Zinn-Oxid (ITO), Indium-Zink-Oxid (IZO) und aluminiumdotiertem Zinkoxid (AZO) gezeigt. Es wurde untersucht, welchen Einfluss verschiedene Prozessparameter wie Energiedichte und Pulszeit des Xenonlichtblitzes, die Absorption der zu behandelnden Schicht, die Gasatmosphäre während der Temperung, die Reflexion im Prozessraum und das Substratmaterial auf die optischen und elektrischen Eigenschaften der Schichten haben. Für ITO-Schichten mit einer Schichtdicke von 150 nm kann der Widerstand von 45 auf <14 Ohm verbessert werden, was vergleichbar mit einer konventionellen Temperung im Umluftofen ist.

Abstract The qualitative and quantitative characteristics of each component layer constituting the structure of organic bulk heterojunction solar cells (OSC-BHJ) contribute significantly towards its overall performance. One of the prevalent issues resulting in reduced device efficiency is due to the conformational inhomogeneities in the active and buffer layers. The mechanical stress, extended thermal exposure and presence of mutually reactive component layers etc., affects negatively on the device stability. Effective methods to address these issues will be extensively benefited by the industry since the current commercialisation of the technology is hindered owing to the lower efficiency and stability of these devices. This dissertation focuses on methods to coherently enhance the performance and longevity of the OSC-BHJ devices. The efficiency enhancements of the devices in this work were achieved through two main routes. The first route was through morphological improvement of the active layer. The second route was through boosting the electrical characteristics of hole transporting conducting polymer layer (HTL) by controlled annealing conditions. The introduction of a suitable additive in the active layer was found to reduce unfavourable phase segregation thus resulting in enhanced morphology. Further, the annealing conditions in different atmospheres (air, nitrogen and vacuum) were found to have a clear influence on the optimum functioning of the HTL in the device. Regarding the stability improvement study done in this work, a method of employing suitable interlayer was developed to effectively abate the internal degradation occurring in the device due to etching reaction on the indium tin oxide (ITO) anode by the HTL. Moreover, experimental investigations were carried out for drawing fundamental understanding of stability degenerating issues such as the influence of mechanical defects on transparent conducting metal oxide (ITO) anode on the performance of the device and heat induced degradations in the low band gap polymer-fullerene active layer. The highlight of this research is that the discovered methods are inexpensive, efficient, and easy to adopt. The results of the study could help the technology to overcome some of its limitations and accelerate its progress towards commercialisation. / Tiivistelmä Orgaanisten heteroliitosaurinkokennojen kerrosrakenteen ominaisuudet ja laatu vaikuttavat merkittävästi aurinkokennojen toiminnallisuuteen. Erityisesti rakenteelliset epähomogeenisuudet aktiivi- ja puskurikerroksissa heikentävät kennon hyötysuhdetta. Kennojen stabiilisuutta tarkasteltaessa myös mekaanisella rasituksella, pitkittyneellä lämpöaltistuksella ja materiaalien reagoinneilla keskenään kerrosten välillä, on selkeä negatiivinen vaikutus kennojen stabiilisuuteen. Orgaanisen aurinkokennoteknologian kaupallistamisen rajoitteina ovat kennojen heikko hyötysuhde ja stabiilisuus, joten menetelmät jotka tarjoavat ratkaisuja edellä mainittuihin ongelmiin, ovat erittäin tärkeitä teknologiaa kaupallistavalle teollisuudelle. Tämä väitöskirja keskittyy johdonmukaisesti selvittämään tapoja, joilla voidaan parantaa heteroliitosaurinkokennojen hyötysuhdetta ja elinikää. Hyötysuhteen tehostamiseksi valittiin kaksi eri lähestymistapaa, joista ensimmäisessä keskityttiin aktiivikerroksen morfologian parantamiseen ja toisessa aukkoja kuljettavan kerroksen sähköisten ominaisuuksien parantamiseen lämpökäsittelyprosessin avulla. Sopivan lisäaineen avulla aktiivikerroksen ei-toivottua kiteytymistä voidaan pienentää ja parantaa näin kerroksen morfologiaa. Lisäksi työssä todettiin, että lämpökäsittelyn aikaisella ympäristöolosuhteella (ilma, typpi, tyhjiö) on merkittävä vaikutus puskurikerroksen optimaaliseen toimintaan aurinkokennossa. Stabiilisuuden parantamiseksi kehitettiin välikerroksen hyödyntämiseen perustuva menetelmä, jolla voidaan tehokkaasti vähentää kennojen sisäisessä rakenteessa tapahtuvaa toiminnallisuuden heikkenemistä, joka aiheutuu aukkoja kuljettavan kerroksen syövyttävästä vaikutuksesta indiumtinaoksidi (ITO) pohjaiseen anodiin. Tämän lisäksi työssä tutkittiin kokeellisesti stabiilisuuteen heikentävästi vaikuttavia tekijöitä, kuten mekaanisen rasituksen aiheuttamia vaurioita metallioksidi (ITO) anodissa ja lämpöaltistuksesta aiheutuvia vikoja polymeeri-fullereeni rakenteeseen perustuvassa aktiivikerroksessa. Tutkimuksen keskeisin tulos on, että esitellyt keinot aurinkokennojen hyötysuhteen ja stabiilisuuden parantamiseen ovat edullisia, tehokkaita ja helppoja hyödyntää. Tulokset voivat merkittävästi edistää orgaanisten aurinkokennojen teknistä kehitystä ja kiihdyttää niiden tuloa kaupallisiksi tuotteiksi.

The rise in the world population can be correlated with an increase in energy need. Fossil fuels are not going to able to cover this need in energy because not only are they limited, they also have a negative effect on the environment. A reason the more to switch renewable energy. One of the most popular renewable energy source is solar energy. The organic solar cell could be a low-cost, light-weight and flexible option for photovoltaics. This thesis will discuss the morphology of the active layer of an organic solar cell. The polymer poly(9,9-dioctylfluorenyl-2,7-diyl) and the fullerene derivate [6,6]-phenyl C61-butyric acid methyl ester were used as model components for the active layer. These two components were processed in different solvents, different ratios, different total concentrations and were either dip- or spin-coated on glass substrates. These samples were analyzed with atomic force microscopy, steady state and time resolved fluorescence and UV/Vis spectroscopy. The analysis show that the morphology of the films processed in chloroform and tetrahydrofuran would react very similar in α-phase and β-phase by dip- and spin-coated samples. Xylene would react the opposite as tetrahydrofuran and chloroform while ethylbenzene would react little with different samples. / De stijging in wereldpopulatie kan gelinkt worden met een stijging in energieverbruik. Het is niet aan te raden om fossiele brandstoffen te gebruiken voor deze energiestijging want niet alleen zijn ze beperkt aanwezig op aarde ook zijn ze niet goed voor het milieu. Een reden te meer om naar duurzame energie over te schakelen. Één van de meeste populaire energiebronnen is zonne-energie. Hierbij zou de organische zonnecel een goedkope, lichte en flexibele optie zijn. Deze thesis zal de morfologie van de actieve laag van een zonnecel bespreken. Het polymeer poly(9,9-dioctylfluorenyl-2,7-diyl) en het fullereen derivaat [6,6]-fenyl C61-butylzuur waren de twee model componenten voor de actieve laag. Deze twee componenten werden in verschillende oplosmiddelen, verschillende verhoudingen en verschillende totaal concentraties bereidt en werden vervolgens gedipcoated of gespincoated op glazen substraten. De stalen werden vervolgens geanalyseerd door atomic force microscopy, steady state en time resolved fluorescence en UV/Vis spectroscopy. De analyse toont dat de morfologie van de films bereidt in chloroform en tetrahydrofuraan gelijkaardig reageren in α- fase en β-fase bij gedipt- en gespincoaten stalen. Terwijl xyleen net omgekeerd reageert als chloroform en tetrahydrofuraan. Bij ethylbenzeen zou de fases maar heel weinig veranderen bij de verschillende stalen.

Philosophiae Doctor - PhD / The objective of the thesis research is to design such vertical handoff decision algorithms in order for mobile field workers and other mobile users equipped with contemporary multimode mobile devices to communicate seamlessly in the NGWN. In order to tackle this research objective, we used fuzzy logic and fuzzy inference systems to design a suitable handoff initiation algorithm that can handle imprecision and uncertainties in data and process multiple vertical handoff initiation parameters (criteria); used the fuzzy multiple attributes decision making method and context awareness to design a suitable access network selection function that can handle a tradeoff among many handoff metrics including quality of service requirements (such as network conditions and system performance), mobile terminal conditions, power requirements, application types, user preferences, and a price model; used genetic algorithms and simulated annealing to optimise the access network selection function in order to dynamically select the optimal available access network for handoff; and we focused in particular on an interesting use case: vertical handoff decision between mobile WiMAX and UMTS access networks. The implementation of our handoff decision algorithm will provide a network selection mechanism to help mobile users select the best wireless access network among all available wireless access networks, that is, one that provides always best connected services to users. / South Africa